Method of manufacturing chemically-pure aluminum by electrolysis



Patented July 22, 1930 UNITED STATES PATENT oFFicE KARL LEO Mnrssnrm, or BERLIN, GERMANY METHOD OF HANU'FACTURING CHEMICALLY-PUBE ALUMINUM BY ELECTROLYSIS m, Drawing. Application filed August 1, 1927, seria1 No. 210,021, and in Germany December 2, 1926.

to a further special electrolytic purification;

According to the process use is made of three layers'located one over another, of which the aluminum to be purified forms the lowermost layer as anode layer, while the purified aluminum presents the uppermost layer as cathode layer. Both layers are separated from one another by means of the electrolyte. In'order to maintain the necessary difference in specific gravities of the three layers, a heavier additionof some kind must be given not only to the electrolyte but also to the anode layer. For this purpose the aluminum to be purified has been alloyed with copper. This had for a result however that the pure aluminum separating on the cathode contained only small traces of iron and silicon, but instead of it copper as substantial impurification. The present invention depends upon the fact of employing as anode layer aluminumpreliminarily prepared with about 99.8 to 99.9% Al according to the-known process already mentioned and further purifying to chemically pure aluminum accordlng to a known process. .In' orderto maintain the necessary specific gravity of the anode layerand to enable its deposition as the lowermost layer, in the process accordingto the present invention copper is not added, which would separate out again in certain quantities in the cathode layer, but inste d of this a difiicultly oxidizable'. precious me al of high specific gravity, as for example gold or platinum or other metals of this group, also, however,

silver or nickel.

Thereby it is most favorable to choose a metal of this kind which'is not taken up by I aluminum in large quantities in solid solution like the copper according to the known process, but which is practically insoluble in solid condition in aluminum. The choice of a metal of specially high specific gravity, as for instance gold or platinum, enables thereby also the amount of addition of this metal to the anode layer for the purpose of increasingthe specific gravity to be kept considerably lower than that possible by the addition of copper. By this means there is the possibil ity further reduced that traces of the alloyed metal separate together with the aluminum on the cathode and thereby again .purify the aluminum. Since the addition of precious remains permanently unchanged in the anode layer, and the anode layer is only renewed 'with' preliminary purified aluminum the process by the use of precious metal is'not uneconomical.

I claim 1. The process of manufacturing chemical ly-pure aluminum'whichv consists in passing a current from an anode through the bath to the cathode, where the anode is heavier than .the electrolyte and consists of. purified alu minum -to which has been added a heavy difiicultly oxidizable metal.

. 2. The process of manufacturing chemically pure aluminum which consists in passing a current from an anode through the bath to the cathode, where the anode is heavier ,than the electrolyte and consists of aluminuni preliminarily purified up to from 99.8

to 99.93pm centto which has been 'addeda heavy diflicultly o'xidizable metal.

3. The process of manufacturing chemical- 1y pure aluminum which consists in passing .a current from an anode through the bath to the c'athode,-where the anode is heavier-than.

the electrolyte and consists of urified aluminum to which has been ad ed a precious metal.

. 4. The rocess of manufacturing chemically pure :1 uminum which consists in assing a current from an anode through the nth to the cathode, where the anode is heavier than the electrolyte and consists of purified aluminum to which has been added gold.

In testimony whereof I afiix hereto my signature.

KARL LEO MEISSNER. 

